A continuing problem with enclosed vehicles is the heat generated by solar energy penetrating to the interior of the vehicle. Depending upon variables such as the season of the year, cloud cover, etc., a vehicle interior may reach temperatures of over 150 degrees Fahrenheit when all windows are up and the vehicle is locked or secured.
The cause of such heat buildup is the well known "greenhouse effect." This effect is due to the fact that standard glass as used in most vehicle windows is transparent to only a limited range of frequencies of electromagnetic energy. Although glass may be transparent to many higher frequencies of solar radiation, this radiation tends to be absorbed by the various interior components of the vehicle, whereupon the radiation energy is re-emitted as lower frequency and energy radiation primarily in the infrared portion of the spectrum. Standard glass is somewhat opaque to such infrared frequencies, and allows only a limited amount of such energy to pass through the glass to the vehicle exterior. Hence, although almost all of the solar energy received by the glass is allowed to pass through, only a fraction of that energy escapes back through the glass. The net energy input to the interior of the vehicle causes the buildup of heat. As newer vehicles, particularly automobiles, have been developed, this problem has become even more serious due to increases in glass area, better insulation which tends to prevent the re-radiation of the heat buildup, and more tightly fitting door, window, and body seals.
What is needed is a device capable of reducing the amount of solar energy penetrating to the vehicle interior, and of controlling the flow of heated air within the vehicle interior when the vehicle is parked and secured. The device must be capable of permanent installation in the vehicle for convenience, and yet easily storable in a permanently installed, compact container.